The goal of this research is to further refine the feline/FIV system as a model for infection of the CNS by lentiviruses. We wish to determine the molecular basis for CNS dysfunctions induced by FIV, define the cell populations infected by the virus, and investigate both direct and indirect mechanisms for virus action. We will perform analyses of a series of wild type and mutant FIVs that exhibit distinct host cell range properties, in order to assess the extent of dissemination of each variant virus int he CNS and periphery, as well as to determine how host cell range properties influence the rate of onset and severity of CNS disease. FIVs to be tested include moleclularly cloned parental FIV-PPR; a mutant of FIV-PPR that lacks a functional deoxyuridine triphosphatase (DU) gene; a natural variant of FIV-PPR that is able to productively infect a glial cell line in vitro, as well as T cells and macrophages; molecularly cloned FIV-34TF10, a species derived from FIV-Petaluma that lacks a functional Orf 2 gene; and a "mutants:" of FIV-034TF10, in which the reading frame for Orf 2 has been repaired. Each of these FIVs has distinct host cell range phenotypes in vitro that may lead to unique mechanisms of action on the CNS. In collaboration with the Fox component, we will use direct serial passage of in vivo infected microglial cells as a means to promote enhanced "neurotropism" of FIV-PPR, a procedure that has been successful for Dr. Fox in selecting for neuroinvasive forms of SIVmac 251. We will also examine the role of indirect effects of viral Env glycoproteins on CNS function by preparing full-length and truncated forms of the Env proteins of FIV-P(PR, FIV-PPRglial, and FIV-34TF10. These proteins will be employed in vivo in the Henriksen component to assess the influence IC inoculation of viral glycoproteins on sleep architecture ina the rat and cat models. The glycoproteins will also be used to determine if exposure to SU will influence transcription patterns in microglia, performed in collaboration with the Sutcliffe component. This component will also provide virological, immunological, and infected cell support for all other components, including the Phillips, Fox, and Sarvetnik components, as well as the Specimen Assessment Core. These studies will further our knowledge of how lentiviruses infect and perturb the CNS.